i have to find the diiference qoutient for f(x)= -x^3 = f(a+h)-f(a)/h

Question

f(x)=-x^3=f(a+h)-f(a)/h

Answer 1

can you write f(a+h) when (a+h) is substituted for x in the definition of f(x)? I hope so. You will need to simplify it after correctly expanding the cube of (a+h), which will consist of FOUR terms (using coefficients 1, 3, 3, 1 from Pascal's triangle.)

 

can you write f(a)? Surely!

 

Subtract the latter result from the former result.  This would be [f(a+h) - f(a)].

 

Now divide the WHOLE THING JUST COMPUTED by h.

 

Note: you need an extra pair of grouping symbols around the difference numerator; your difference quotient attempt would not be correct because h would divide only into f(a), according to PEMDAS rules.